Magnetic resonance imaging (MRI) is a method of imaging information within a living body using nuclear magnetic resonance phenomenon. Furthermore, the f-MRI has recently been developed. The f-MRI stands for functional magnetic resonance imaging, and is one of the methods of imaging brain functions using MRI. The changes in the neuronal activities in local areas of the brain result in the changes in the nuclear magnetic resonance imaging signals, which is the principle of the f-MRI.
Furthermore, the electroencephalogram (EEG) for living bodies has conventionally been performed. A number of simultaneous electroencephalogram (EEG) and f-MRI measurements have recently been conducted in research institutes worldwide for living humans. For example, Patent Reference 1 discloses a helmet for electroencephalogram measurement for humans. Patent Reference 2 discloses an electrode for electroencephalogram measurement for humans.
Meanwhile, with small animals such as rats, which have smaller brain volume than humans, large electrodes disclosed in Patent References 1 and 2 cannot be used. With EEG for small animals, it is difficult to fasten small electrodes to limited brain space, and it is also difficult to maintain low impedance generated between the scalp and the electrodes. Consequently, few reports have been made on simultaneous EEG and f-MRI measurement techniques for small animals due to such technical difficulties.
With the conventional simultaneous EEG and f-MRI measurement techniques for small animals, the metal or carbon electrode was only placed and fastened to the brain surface of small animal, which is why there are only a few successful examples of simultaneous EEG and f-MRI measurements for small animal (such as rat and mouse) (See Non-patent References 1 and 2). Furthermore, since EEG measurement in such EEG-f-MRI measurement uses a single electrode (See Non-patent Reference 1), electroencephalogram can be detected only partially and it is therefore not effective when the target of study is the entire brain.
Patent References 3 and 4 disclose systems using a plurality of measurement lines or electrodes for EEG.